Diagnostic-quality X-ray computed tomography (CT) images, with spatial resolution of 0.05 to 0.1 mm, have now been made of small laboratory animals with a "micro-CT" system incorporating a patented, high-resolution X-ray detector. A demonstration of the utility of the micro-CT approach in three important areas of bio-medical research and practice is now proposed: 1) In vivo detection of tumors in small rodents (tumors were seen in CT images of mice during Phase I) could save time and money in expensive carcinogenesis bioassays, and could also be used to quantify tumor regression in chemotherapy trials. 2) Scanning of tissue biopsy samples from human patients (for ascertaining completeness of tumor removal during extirpatory surgery) might be accomplished faster than conventional frozen-section inspection, thus reducing time, expense, and patient risk. 3) Micro-CT inspection could provide a new dimension to experimental teratology by allowing researchers to follow development of birth defects in rodent embryos in utero, in vivo throughout the course of experiments. Experiments in each of these areas, using an improved scanner, will determine detection thresholds. Tumor-detection enhancement through use of monoclonal antibodies will be studied as well. This work will result in designs for commercial scanning instruments for medical laboratories.